Being right matters: Model-compliant events in predictive processing.

While prediction errors (PE) have been established to drive learning through adaptation of internal models, the role of model-compliant events in predictive processing is less clear. Checkpoints (CP) were recently introduced as points in time where expected sensory input resolved ambiguity regarding the validity of the internal model. Conceivably, these events serve as on-line reference points for model evaluation, particularly in uncertain contexts. Evidence from fMRI has shown functional similarities of CP and PE to be independent of event-related surprise, raising the important question of how these event classes relate to one another. Consequently, the aim of the present study was to characterise the functional relationship of checkpoints and prediction errors in a serial pattern detection task using electroencephalography (EEG). Specifically, we first hypothesised a joint P3b component of both event classes to index recourse to the internal model (compared to non-informative standards, STD). Second, we assumed the mismatch signal of PE to be reflected in an N400 component when compared to CP. Event-related findings supported these hypotheses. We suggest that while model adaptation is instigated by prediction errors, checkpoints are similarly used for model evaluation. Intriguingly, behavioural subgroup analyses showed that the exploitation of potentially informative reference points may depend on initial cue learning: Strict reliance on cue-based predictions may result in less attentive processing of these reference points, thus impeding upregulation of response gain that would prompt flexible model adaptation. Overall, present results highlight the role of checkpoints as model-compliant, informative reference points and stimulate important research questions about their processing as function of learning und uncertainty.

Graph measures in task-based fMRI: Functional integration during read-out of visual and auditory information.

This study investigated how attending to auditory and visual information systematically changes graph theoretical measures of integration and functional connectivity between three network modules: auditory, visual, and a joint task core. Functional MRI BOLD activity was recorded while healthy volunteers attended to colour and/or pitch information presented within an audiovisual stimulus sequence. Network nodes and modules were based on peak voxels of BOLD contrasts, including colour and pitch sensitive brain regions as well as the dorsal attention network. Network edges represented correlations between nodes' activity and were computed separately for each condition. Connection strength was increased between the task and the visual module when participants attended to colour, and between the task and the auditory module when they attended to pitch. Moreover, several nodal graph measures showed consistent changes to attentional modulation in form of stronger integration of sensory regions in response to attention. Together, these findings corroborate dynamical adjustments of both modality-specific and modality-independent functional brain networks in response to task demands and their representation in graph theoretical measures.

Dissociating predictability, plausibility and possibility of sentence continuations in reading: evidence from late-positivity ERPs.

Late positive event-related potential (ERP) components occurring after the N400, traditionally linked to reanalysis due to syntactic incongruence, are increasingly considered to also reflect reanalysis and repair due to semantic difficulty. Semantic problems can have different origins, such as a mismatch of specific predictions based on the context, low plausibility, or even semantic impossibility of a word in the given context. DeLong, Quante & Kutas (2014) provided the first direct evidence for topographically different late positivities for prediction mismatch (left frontal late positivity for plausible but unexpected words) and plausibility violation (posterior-parietal late positivity for implausible, incongruent words). The aim of the current study is twofold: (1) to replicate this dissociation of ERP effects for plausibility violations and prediction mismatch in a different language, and (2) to test an additional contrast within implausible words, comparing impossible and possible sentence continuations. Our results replicate DeLong, Quante & Kutas (2014) with different materials in a different language, showing graded effects for predictability and plausibility at the level of the N400, a dissociation of plausible and implausible, anomalous continuations in posterior late positivities and an effect of prediction mismatch on late positivities at left-frontal sites. In addition, we found some evidence for a dissociation, at these left-frontal sites, between implausible words that were fully incompatible with the preceding discourse and those for which an interpretation is possible.

Predictability, plausibility, and two late ERP positivities during written sentence comprehension.

Van Petten and Luka's (2012, International Journal of Psychophysiology, 83(2), 176-190) literature survey of late positive ERP components elicited by more or less predictable words during sentence processing led them to propose two topographically and functionally distinct positivities: a parietal one associated with semantically incongruent words related to semantic reanalysis and a frontal one with unknown significance associated with congruent but lexically unpredicted words. With the goal of testing this hypothesis within a single set of experimental materials and participants, we report results from two ERP studies: Experiment 1, a post-hoc analysis of a dataset that varied on dimensions of both cloze probability (predictability) and plausibility, and Experiment 2, a follow-up study in which these factors were manipulated in a controlled fashion. In both studies, we observed distinct post-N400 positivities: a more anterior one to plausible, but not anomalous, low cloze probability sentence medial words, and a more posterior one to semantically anomalous sentence continuations. Taken together with an observed canonical cloze-modulated N400, these dual positivities indicate a dissociation between brain processes relating to written words׳ sentential predictability versus plausibility, clearly an important distinction for any viable neural or psycholinguistic model of written sentence processing.